Method for continuous production of a perfluoroalkyl iodide telomer

ABSTRACT

The present invention relates to a process for continuously producing a perfluoroalkyl iodide represented by the general formula R f (CF 2 CF 2 ) n I, wherein R f  is a C 1-6  perfluoroalkyl and n is an integer from 1 to 4, the method comprising continuously supplying a perfluoroalkyl iodide as a telogen represented by the general formula R f I, wherein R f  is as defined above, and tetrafluoroethylene as a taxogen to a tubular reactor packed with a metal catalyst comprising a powdery spherical metal or a sintered metal; and conducting telomerization at a temperature of 60 to 160° C. under a pressure of 0.1 to 5 MPa (gauge pressure).  
     According to the present invention, medium-chain perfluoroalkyl iodides can be continuously and efficiently produced with little generation of impurities, such as hydrogen-containing organic compounds and the like.

TECHNICAL FIELD

[0001] The present invention relates to a continuous production processfor perfluoroalkyl iodide telomers.

BACKGROUND OF THE INVENTION

[0002] Perfluoroalkyl iodides having about 6 to 12 carbon atoms areuseful as ingredients for surfactants and for water- and oil-repellentsfor fibers.

[0003] For the production of perfluoroalkyl iodides, industriallyemployed are processes using telomerization as shown in the followingreaction formula:

R_(f)I+nCF₂═CF₂→R_(f)(CF₂CF₂)_(n)I

[0004] wherein R_(f) is a perfluoroalkyl having 1 to 6 carbon atoms andn is an integer from 1 to 4.

[0005] This reaction is known to proceed with heating. German PatentPublication No. 1,443,517, for example, discloses a method wherein areaction is conducted at a temperature of 250 to 800° C. under apressure of 2 mmHg to 5 atmospheres with a residence time of 1 hour orless. Such a thermal reaction, however, poses a problem with theproduction of large amounts of perfluoroalkanes, which are the dimerizedproducts of the perfluoroalkyl radicals generated in the reaction.

[0006] Japanese Unexamined Patent Publication No. 305995/1994 disclosesa method of thermal telomerization at a high temperature of about 300 to360° C. In this method, generated are by-products such as iodine andperfluoroalkanes produced by the reactions among the telomers.Especially due to the generation of iodine, reactor corrosion, cloggingof pipes and similar components, and other problems are likely to occur.Furthermore, the introduction of tetrafluoroethylene as a taxogen athigh temperatures poses a safety problem.

[0007] Meanwhile, a variety of catalysts have been developed to conducttelomerization at lower temperatures.

[0008] For example, UK Patent No. 1,535,408, U.S. Pat. No. 5,068,471,etc., disclose processes of telomerization through the use offree-radical generators. In these processes, however, perfluoroalkylradicals react with the free-radical generators and produce, asby-products, hydrogen-containing organic compounds represented byR_(f)H, wherein R_(f) is a C₁₋₆ perfluoroalkyl.

[0009] To avoid the generation of undesired long-chain telomers(compounds represented by the formula R_(f)(CF₂CF₂)_(n)I, where n is 5or more), the concentration of starting telogens (R_(f)I) is generallyincreased and the concentration of taxogens is decreased. As a result,the conversion to the desired medium-chain telomers (compoundsrepresented by the formula R_(f)(CF₂CF₂)_(n)I, where n is 1 to 4) islow, and the starting telogens (R_(f)I) are recycled by distillation.

[0010] However, it is difficult to separate the by-product (i.e.,R_(f)H) from the starting compound (i.e., R_(f)I). Thus, whentelomerization is continuously carried out, R_(f)H causes a disadvantageof decreasing reaction efficiency due to its accumulation in thetelogen.

[0011] Chen, et al., (Preliminary Note, Journal of Fluorine Chemistry 36(1987), pp. 483-489) disclose the use of copper powder as a catalyst fortelomerization. This reaction proceeds at a low temperature of 80 to100° C., and moreover, is advantageous for achieving a reaction timethat is shorter than that of telomerization conducted at hightemperatures.

[0012] Japanese Unexamined Patent Publication No. 239335/1996 describeszinc, magnesium, vanadium, rhenium, rhodium, ruthenium, platinum andsilver as telomerization catalysts. Moreover, Japanese Unexamined PatentPublication No. 239336/1996 and other publications disclose, incopper-catalyzed telomerization, a method employing other transitionmetal as a co-catalyst.

[0013] However, even when the aforementioned various catalysts are used,their catalytic activities are still insufficient, and the selectivityfor medium-chain telomeric compounds, in which n is 4 or smaller, isalso unsatisfactory.

DISCLOSURE OF THE INVENTION

[0014] A primary object of the present invention is to provide a processfor producing medium-chain perfluoroalkyl iodides throughtelomerization, said process being an industrially advantageous processenabling the continuous and efficient production of medium-chainperfluoroalkyl iodides at low temperatures and generating fewimpurities, such as hydrogen-containing organic compounds and the like.

[0015] The inventors conducted extensive research to achieve the aboveobjective and found as a result that medium-chain telomers can becontinuously and efficiently produced in a short period of time at arelatively low temperature with little impurity generation according toa telomerization method wherein a telogen and a taxogen used as startingcompounds are supplied to a tubular reactor packed with a metal catalystcomprising a powdery spherical metal or a sintered metal. The presentinvention has been accomplished based on the finding.

[0016] In particular, the present invention provides a continuousproduction process for perfluoroalkyl iodides as described below:

[0017] 1. A process for continuously producing a perfluoroalkyl iodiderepresented by the general formula

R_(f)(CF₂CF₂)_(n)I

[0018] wherein R_(f) is a C₁₋₆ perfluoroalkyl and n is an integer from 1to 4,

[0019] the method comprising:

[0020] continuously supplying a perfluoroalkyl iodide as a telogenrepresented by the general formula

R_(f)I

[0021] wherein R_(f) is as defined above, and tetrafluoroethylene as ataxogen to a tubular reactor packed with a metal catalyst comprising apowdery spherical metal or a sintered metal; and

[0022] conducting telomerization at a temperature of 60 to 160° C. undera pressure of 0.1 to 5 MPa (gauge pressure).

[0023] 2. A process according to Item 1, wherein the metal catalyst is apowdery spherical metal having an average particle diameter of 1 to 200μm.

[0024] 3. A process according to Item 1, wherein the metal catalyst is asintered metal composed of metal component having an average particlediameter of 50 μm to 0.5 mm.

[0025] 4. A process according to Item 1, wherein the reaction space ofthe tubular reactor has a length/diameter ratio of 5 to 1,000.

[0026] 5. A process according to Item 1, wherein a solution iscontinuously supplied to the reactor to conduct telomerization, saidsolution being obtained by dissolving tetrafluoroethylene as a taxogenin the perfluoroalkyl iodide as a telogen. 6. A process according toItem 1, wherein the metal catalyst is a powdery spherical metal or asintered metal, the catalyst comprising copper metal, tin metal, or tinmetal mixed with copper as a co-catalyst.

[0027] The production process of the invention is a process to produce aperfluoroalkyl iodide represented by the general formulaR_(f)(CF₂CF₂)_(n)I, wherein R_(f) is a C₁₋₆ perfluoroalkyl and n is aninteger from 1 to 4, by subjecting a perfluoroalkyl iodide as a telogenrepresented by the general formula R_(f)I, wherein R_(f) is as definedabove, to reaction with tetrafluoroethylene as a taxogen.

[0028] In the process of the invention, a tubular reactor packed with ametal catalyst comprising a powdery spherical metal or a sintered metalis used as a reactor. Telomerization is conducted by continuouslysupplying to this reactor a perfluoroalkyl iodide as a telogenrepresented by the general formula R_(f)I, wherein R_(f) is as definedabove, and tetrafluoroethylene as a taxogen.

[0029] Tubular reactors usable herein include those having acylindrical, elongated reaction space, preferably those with alength/inner diameter ratio of about 5 to about 1,000, and morepreferably those with a length/inner diameter ratio of about 10 to about200. The cross-sectional area of the reaction space of the tubularreactor may generally have, although not limited to, a free passagecross-section of about 1 to about 100 cm². An excessively large diameterof a tubular reactor is not preferable because reaction heat accumulatesin the reactor, thereby making control of telomerization difficult. Anexcessive rate in supplying the starting compounds is not preferablebecause the amount of unreacted taxogens is likely to increase. Examplesof materials for the tubular reactor include, although are not limitedto, stainless steel, copper, Hastelloy, glass lining, etc.

[0030] A powdery spherical metal or a sintered metal is used as acatalyst to be packed into the tubular reactor. When the powderyspherical metal is used, the average particle diameter thereof ispreferably about 1 to about 200 μm, and more preferably about 10 toabout 45 μm. Such a powdery spherical metal has, for example, anapparent density of about 4.6 to about 5.5 g/cm³ and thus is ahigh-density catalyst of low porosity. In the sintered metal, theaverage particle diameter of the metal particles used for the sinteredmetal is preferably from about 1 μm to about 0.5 mm, and more preferablyabout 100 μm to about 0.1 mm. Although the shape of the sintered metalis not limited, an excessively large sintered body results in decreasein metal amount to be packed into a reactor. Usually, the sintered metalmay have a rod-like form having a diameter of about 1 to about 20 mm anda length of about 1 to about 100 mm. The sintered metal is, as with thepowdery spherical metal, a highly-dense, hardly-deformable catalyst.

[0031] As opposed to the powdery spherical metal and sintered metal inthe above-described forms, metal catalysts in the form of, for example,flakes, electrolytic powder or the like have a low apparent density andare porous. The use of these catalysts is not preferable because thecatalysts may be compressed during telomerization, thereby generatinghigh pressure in the intake port of the tubular reactor and tending tohinder the supply of the starting materials.

[0032] Types of metal catalysts are not limited insofar as theypractically exhibit catalytic action to the aforementionedtelomerization. Examples of such metals usable herein are copper, tin,zinc, magnesium, vanadium, rhenium, rhodium, ruthenium, platinum,silver, alloys of these metals, mixtures of these metals, etc. Further,alloys made of any of these metals with small amounts of othertransition metal can also be used. Transition metals usable hereininclude metals that exhibit by themselves no catalytic action or verysmall catalytic action, such as iron, nickel, chromium, molybdenum,tungsten, titanium, etc.

[0033] In particular, when copper, tin, or tin mixed with copper as aco-catalyst is used as a catalyst, catalytic activity and selectivityfor medium-chain telomers are improved. In addition, the use of tinmixed with copper as a co-catalyst costs less than the use of copperalone. Further, a copper-tin alloy has a melting point lower than thatof copper, providing an advantage of easier production of sinteredbodies. A mixture of tin powder and copper powder, tin-copper alloy, andthe like are usable as the tin mixed with copper as a co-catalyst. Bothtin and copper can be used as a catalyst for telomerization, andtherefore the proportion thereof can be selected at will. Also usableare, for example, commercially available bronze powder, which hasexcellent moldability, sintering properties, strength and otherproperties, and an alloy having a copper proportion of 90 mass % and atin proportion of 10 mass %.

[0034] In the production process of the invention, for example,tetrafluoroethylene as a taxogen is dissolved in a perfluoroalkyl iodideas a telogen, and the resulting solution is supplied to the reactorthrough an intake port to bring the solution in contact with the metalcatalyst packed into the reactor, thereby enabling telomerization toproceed continuously. This reaction is a liquid-solid two-phasereaction. The telomer generated by telomerization is in the liquid statein the reactor, and it can be separated from the metal catalyst throughliquid-solid separation using a filter or other means adjacent to theexit port of the tubular reactor, and discharged from the reactor.

[0035] Telogens to be used as starting compounds are represented by theabove-described general formula R_(f)I. Specific examples thereof are2-iodoperfluoropropane, 1-iodoperfluoroethane, 1-iodoperfluorobutane,1-iodoperfluorohexane, etc. These telogens can be used alone or incombination of two or more species.

[0036] Among these telogens, when 1-iodoperfluorobutane or1-iodoperfluorohexane is used, reaction speed is increased 1.4 times or3.0 times, compared with the reaction speed obtained by the use of1-iodoperfluoroethane. Therefore, these lower telogens may be used aloneor in combination in the present invention.

[0037] The reaction temperature is preferably in a range of about 60 toabout 160° C. and more preferably about 100 to about 140° C. Excessivelylow reaction temperatures are not preferable due to insufficientreaction speed. On the other hand, when reaction temperatures exceed therange described above, although telomerization progresses, they increasea cost and a risk to safety.

[0038] The pressure during the reaction is preferably in a range ofabout 0.1 to about 5 MPa (gauge pressure). Although the reactionprogresses under a pressure that is below the range specified above, itis not preferable due to decreased space-time yields. On the other hand,when the reaction pressure exceeds the aforementioned range, althoughtelomerization progresses, it increases a cost and a risk to safety.

[0039] In the production process of the invention, the rate of feedingthe telogen and taxogen, the rate of discharging the reaction solution,the amount of catalysts used, etc., can be readily selected byconducting preliminary experiments.

[0040] Although the ratio of telogen to taxogen, contact time, etc., cannot be generalized because they depend on the types of startingcompounds, mixing ratio, reaction time and so on, preferable results canbe obtained from a tetrafluoroethylene concentration(tetrafluoroethylene/(tetrafluoroethylene+telogen)) of about 1 to about15 mol % and a catalyst contact time of about 10 seconds to about 9minutes.

[0041] In the production process of the invention, complicatedoperations for recycling metal catalysts are not required, andgeneration of long-chain telomers is inhibited by controlling the amountof telogen and taxogen to be supplied, thereby easily enabling anincrease in selectivity for the desired medium-chain telomers (n=1 to5). Moreover, as the reaction solution discharged from the reactor doesnot contain metal catalysts, the desired product can therefore bereadily isolated therefrom by distillation or like procedure withoutseparation/recovery of the metal catalysts.

[0042] As described above, according to the production process of theinvention, the desired product, i.e., medium-chain telomers, can becontinuously and efficiently produced at relatively low temperatures.Thus, it is an industrially advantageous process in producingmedium-chain telomers.

BEST MODE FOR CARRYING OUT THE INVENTION

[0043] Examples are given below to describe the invention in moredetail.

EXAMPLE 1

[0044] A stainless-steel tube with an external diameter of ⅜ inches thatwas packed with 46 g of spherical copper powder (produced by MitsuiMining & Smelting Co., Ltd., particle size: 330 mesh or less, averageparticle diameter: 19 μm) was used as a tubular reactor. A startingsolution wherein tetrafluoroethylene (TFE) was dissolved in aperfluoroethyl iodide (TFE concentration: TFE/(telogen+TFE)=4.25 mol %)was continuously supplied to the stainless-steel tube to conducttelomerization under a reaction pressure of 3 MPa (gauge pressure) at astarting solution supply rate of 9.0 ml/min. The reaction was conductedat a temperature ranging from 60 to 120° C.

[0045] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components.Results are shown in Table 1. TABLE 1 Component distribution in product(mol %) Reaction n Value (C₂F₅(CF₂CF₂)_(n)I) TFE tempera- Moreconversion ture (° C.) 0 1 2 3 4 than 4 (%) 60 99.66 0.25 0.056 0.01630.0068 0.0109 17.59 80 99.7 0.25 0.029 0.0091 0.0036 0.0083 21.59 10099.56 0.37 0.049 0.012 0.0041 0.0049 28.36 120 99.34 0.55 0.084 0.0200.0047 0.0213 47.55 140 98.87 0.94 0.15 0.029 0.0054 0.0056 59.7

EXAMPLE 2

[0046] A stainless-steel tube with an external diameter of ⅜ inches thatwas packed with 46 g of spherical copper powder (produced by MitsuiMining & Smelting Co., Ltd., particle size: 330 mesh or less, averageparticle diameter: 19 μm) was used as a tubular reactor. A startingsolution wherein tetrafluoroethylene (TFE) was dissolved in aperfluoroethyl iodide (TFE concentration: 4.25 mol %) was continuouslysupplied to the stainless-steel tube to conduct telomerization under areaction pressure of 3 MPa (gauge pressure) at a reaction temperature of120° C. in a reaction volume of 4 ml. The starting solution was suppliedat a rate of 1.4 ml/min, 4.4 ml/min or 9 ml/min.

[0047] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components.Results are shown in Table 2. TABLE 2 Rate of supplying Componentdistribution in product (mol %) the starting n Value (C₂F₅(CF₂CF₂)_(n)I)TFE solution More conversion (ml/min) 0 1 2 3 4 than 4 (%) 1.4 83.1114.89 1.66 0.27 0.059 0.011 99.89 4.4 84.32 13.34 1.84 0.39 0.087 0.41380.14 9.0 99.34 0.55 0.084 0.020 0.0047 0.0213 47.55

EXAMPLE 3

[0048] A stainless-steel tube with an external diameter of ⅜ inches thatwas packed with 18 g of spherical copper powder (produced by MitsuiMining & Smelting Co., Ltd., particle size: 330 mesh or less, averageparticle diameter: 19 μm) was used as a tubular reactor. A startingsolution wherein tetrafluoroethylene (TFE) was dissolved inperfluoroethyl iodide was continuously supplied to the stainless-steeltube to conduct telomerization under a reaction pressure of 4.5 MPa(gauge pressure) at a starting solution supply rate of 4.4 ml/min and areaction temperature of 120° C. The concentration of tetrafluoroethylene(TFE) in the starting solution was 3.03 mol %, 7.06 mol %, 8.42 mol % or11.35 mol %.

[0049] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components.Results are shown in Table 3. TABLE 3 Component distribution in product(mol %) TFE n value (C₂F₅(CF₂CF₂)_(n)I) TFE concentration Moreconversion (mol %) 0 1 2 3 4 than 4 (%) 3.03 99.71 0.27 0.028 0.002 — —10.54 7.06 98.32 1.29 0.3 0.07 0.02 — 28.68 8.42 97.74 1.65 0.44 0.120.03 0.02 33.37 11.35 96.47 2.37 0.75 0.26 0.09 0.06 41.25

EXAMPLE 4

[0050] A stainless-steel tube with an external diameter of ⅜ inches thatwas packed with 18 g of spherical copper powder (produced by MitsuiMining & Smelting Co., Ltd., particle size: 330 mesh or less, averageparticle diameter: 19 μm) was used as a tubular reactor. A startingsolution wherein tetrafluoroethylene (TFE) as a taxogen was dissolved ina telogen, i.e., perfluoroethyl iodide, perfluorobuthyl iodide orperfluorohexyl iodide (TFE concentration: 3.14 mol %) was continuouslysupplied to the stainless-steel tube to conduct telomerization under areaction pressure of 4.5 MPa (gauge pressure) at a starting solutionsupply rate of 8.3 ml/min and a reaction temperature of 120° C.

[0051] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components.Results are shown in Table 4. TABLE 4 n Value of Component distributionin product (mol %) Rate of TFE starting n Value (C₂F₅(CF₂CF₂)_(n)I) dis-telomer*¹ 0 1 2 3 4 5 appearance*² 0 99.62  0.34 0.042 0.0046 — —0.000665 1 — 99.62 0.35 0.029 — — 0.000922 2 — — 98.71 1.16 0.11 0.0130.00194

EXAMPLE 5

[0052] As a metal catalyst, 63.9 g of spherical copper powder (producedby Fukuda Metal Foil Powder Co., Ltd., average particle diameter: 100μm), 59.4 g of spherical copper-tin alloy (copper: 90 mass %, tin: 10mass %) (produced by Fukuda Metal Foil Powder Co., Ltd., averageparticle diameter: 200 μm) or 28.4 g of spherical tin powder (producedby Kishida Chemical Co., Ltd., average particle diameter: 75 μm) wasused and packed into a stainless-steel tube with an external diameter of⅜ inches.

[0053] A solution wherein tetrafluoroethylene (TFE) was dissolved inperfluoroethyl iodide (TFE concentration: 9.4 mol %) was used as astarting solution, and continuously supplied to the stainless-steel tubeto conduct telomerization under a reaction pressure of 3.0 MPa (gaugepressure) at a starting solution supply rate of 2.0 ml/min and areaction temperature of 120° C.

[0054] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components. Thesurface area of the metal catalysts was measured by a surface areaanalyzer (Yuasa-Ionics Co., Ltd.)

[0055] Table 5 shows the results. TABLE 5 TFE decrease rate Catalyst TFEper m² Surface TFE decrease of catalyst Amount area conversion ratesurface area Type used (g) (m²/g) (%) (mol/s) (mol/s · m²) Copper-tin59.44 0.012 24.5 0.0028 3.93E−03 alloy Copper powder 63.88 0.044 40.60.006 2.13E−03 Tin powder 28.36 0.191 93.5 0.0132 2.44E−03

EXAMPLE 6

[0056] A stainless-steel tube with an external diameter of {fraction(6/8)} inches that was packed with 118 g of a sintered metal (diameter:1 mm, length: 10 mm) of spherical copper powder was used as a tubularreactor. A starting solution wherein tetrafluoroethylene (TFE) wasdissolved in perfluoroethyl iodide (TFE concentration: 10 mol %) wascontinuously supplied to the stainless-steel tube to conducttelomerization under a reaction pressure of 4.5 MPa (gauge pressure) ata reaction temperature of 120° C. and a starting solution supply rate of2 ml/min, 3 ml/min or 5 ml/min.

[0057] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components. Theresults are shown in Table 6. TABLE 6 Rate of supplying the startingComponent distribution in product (mol %) TFE solution n Value(C₂F₅(CF₂CF₂)_(n)I) conversion (ml/min) 0 1 2 3 4 More than 4 (%) 297.65 1.62 0.48 0.16 0.04 0.04 60.4 3 98.55 1 0.3 0.1 0.03 0.02 28.9 599.93 0.49 0.14 0.04 — — 1.45

EXAMPLE 7

[0058] A stainless-steel tube with an external diameter of {fraction(6/8)} inches that was packed with 184 g of spherical copper powder(produced by Mitsui Mining & Smelting Co., Ltd., particle size: 330 meshor less, average particle diameter: 19 μm) was used as a tubularreactor. A starting solution wherein tetrafluoroethylene (TFE) wasdissolved in perfluoroethyl iodide (TFE concentration: 10 mol %) wascontinuously supplied to the stainless-steel tube to conducttelomerization under a reaction pressure of 4.5 MPa (gauge pressure) ata reaction temperature of 120° C. and a starting solution supply rate of4.2 ml/min.

[0059] The reaction solution discharged from the stainless-steel tubewas cooled and analyzed by gas chromatography for its components.Results are shown in Table 7.

COMPARATIVE EXAMPLE 1

[0060] Into a stainless-steel, 230-ml pressurized mixing vessel reactorequipped with a stirrer, 400 g of 1-iodoperfluoroethane and 184 g ofspherical copper powder (produced by Mitsui Mining & Smelting Co., Ltd.,particle size: 330 mesh or less, average particle diameter: 19 μm) werecharged. A starting solution wherein tetrafluoroethylene (TFE) wasdissolved in perfluoroethyl iodide (TFE concentration: 10 mol %) wassupplied to the reactor to continuously conduct telomerization under areaction pressure of 1.9 MPa (gauge pressure) at a reaction temperatureof 120° C. and a starting solution supply rate of 2.3 ml/min.

[0061] The reaction solution thus obtained was cooled and analyzed bygas chromatography for its components. Results are shown in Table 7.TABLE 7 Component distribution in product (mol %) TFE TFE Reaction nValue (C₂F₅(CF₂CF₂)_(n)I) conversion Reactor (mol %) time (min) 0 1 2 34 5 (%) Ex. 7 Tubular 10 8.3 93.15 5.5 0.97 0.26 0.069 0.048 93.8 CompVessel 10.3 100 94.13 4.49 1.03 0.26 0.06 0.03 92.3 Ex. 1

1. A process for continuously producing a perfluoroalkyl iodiderepresented by the general formula R_(f)(CF₂CF₂)_(n)I wherein R_(f) is aC₁₋₆ perfluoroalkyl and n is an integer from 1 to 4, the methodcomprising: continuously supplying a perfluoroalkyl iodide as a telogenrepresented by the general formula R_(f)I wherein R_(f) is as definedabove, and tetrafluoroethylene as a taxogen to a tubular reactor packedwith a metal catalyst comprising a powdery spherical metal or a sinteredmetal; and conducting telomerization at a temperature of 60 to 160° C.under a pressure of 0.1 to 5 MPa (gauge pressure).
 2. A processaccording to claim 1, wherein the metal catalyst is a powdery sphericalmetal having an average particle diameter of 1 to 200 μm.
 3. A processaccording to claim 1, wherein the metal catalyst is a sintered metalcomposed of metal component having an average particle diameter of 50 μmto 0.5 mm.
 4. A process according to claim 1, wherein the reaction spaceof the tubular reactor has a length/diameter ratio of 5 to 1,000.
 5. Aprocess according to claim 1, wherein a solution is continuouslysupplied to the reactor to conduct telomerization, said solution beingobtained by dissolving tetrafluoroethylene as a taxogen in theperfluoroalkyl iodide as a telogen.
 6. A process according to claim 1,wherein the metal catalyst is a powdery spherical metal or a sinteredmetal, the catalyst comprising copper metal, tin metal, or tin metalmixed with copper as a co-catalyst.